Voice-over Internet Protocol (VoIP) is a protocol optimized for the transmission of voice through the Internet or other packet-switched networks. VoIP allows users to use regular telephone networks anywhere through any Internet service provider. VoIP systems carry telephony signals as digital audio encapsulated in a data-packet stream over IP by converting analog audio signals to digital data that can be transmitted over the Internet. VoIP devices (e.g., terminal adapters, SIP phones, Media Gateways) are able to convert analog signals to digital signals encapsulated in the packets to be transmitted over the Internet.
VoIP may experience some time delays as a result of physical distance, the number of router hops, encryption and voice/data conversion. A typical packet will be forwarded over many links via many gateways, each of which will not begin to forward the packet until it has been completely received. Processing delays are incurred while a gateway determines what to do with a newly received packet. Small delays are generally not noticeable by users, but larger delays may result in a degradation of voice quality. Thus, it is desirable to measure processing delays associated with VoIP devices to determine whether processing delays added by VoIP devices are acceptable.
However, current measuring techniques use different tools to measure VoIP performance in the analog and IP domains, which makes it difficult to determine the time it takes for a VoIP device to convert an analog event into an IP event and vice versa. Thus, a method for accurately determining processing delays added by VoIP devices to end-to-end transmission delays and post-dialing delays may be beneficial to determine whether they are degrading the end-to-end performance of VoIP calls. Any company providing VoIP services or developing VoIP products may use the technique to assess the company's equipment performance.